This invention relates to beach building and the related function of preventing shoreline erosion due to wave action. More particularly, the invention relates to a beach restoration structure which is placed in relatively shallow water a small distance from the shoreline, the structure being readily transportable to the shore site and adapted to be assembled in side-by-side relation with other units, in a partly submerged condition to define an off shore barrier.
Shorelines and beaches are subject to erosion from the action of waves impinging thereon. Wave action erodes beaches by several different mechanisms. Waves mobilize shoreline materials and then redistribute them. Shoreline structures including sea walls, pilings, etc. often increase beach erosion by causing wave reflection, turbulence, eddies and currents. These conditions mobilize the beach material which may be transported offshore, thus destroying the existing beach. Further, heavy storms can impinge high waves on beaches and shorelines imparting heavy forces which carry away the beach material and crumble the shoreline leading to catastrophic erosion.
In a natural beach/water ecosystem, the shallow water extending up to the beach and the beach face itself act to dissipate the energy of the waves, thereby preventing erosion of the land behind the beach. Typical waterfront profiles include (1) a surf zone of relatively shallow water where the waves break into surf, (2) a beach zone where a wave expends its last landward energy, and (3) the land behind the beach. During severe storm conditions when the waves are commonly two to three times their normal height or more, the typical result is the loss of material from the beach zone.
Many methods have been employed in an attempt to reduce shoreline erosion. These attempts have included both protruding and submerged breakwaters located offshore. The protruding breakwater reflects and/or dissipates the waves. A submerged breakwater either reflects and/or dissipates waves, or causes the waves to break further offshore. These breakwaters are typically constructed of concrete or stone and are solid structures, commonly rubble or rocks are piled in a line offshore to form a breakwater.
Breakwaters have several deficiencies. First of all, they are expensive to build and maintain. Rubble breakwaters erode by losing rock to the action of waves and unstable subsoils commonly cause the rocks or concrete segments to sink into the sea or lake bed. Wave action scours and undercuts the base of the breakwater and eventually causes portions to topple outward, thus rendering the structure useless.
Typically, these breakwater structures are built close enough to the shore for waves to come crashing in and hit with full force. The wall stops the forward movement of the wave and the wave ruptures transforming the forward energy of the wave into an equivalent level of vertical energy. The fraction of the wave deflected downward drives into the bottom material and the result is similar to directing a fire hose at the base of a wall causing scour and undercutting.
Revetments and sea walls are also used to reduce shoreline erosion. However, these structures actually inhibit beach formation. Although they may protect the shore behind the beach, they tend to erode the beach by creating intensified water currents which may permanently transport beach material away from the shore.
The unique beach building structure of the present invention resolves the difficulties described above and affords other features and advantages heretofore not obtainable.